Touch screen and electronic device having the same

ABSTRACT

A touch screen includes a touch panel and an ultrasonic probe. A touch panel includes a cover plate, a first sensing structure including a plurality of receiving electrode lines, and a second sensing structure including a plurality of transmitting electrode lines. The ultrasonic probe includes a first piezoelectric film and a second piezoelectric film. The first piezoelectric film is attached to the touch panel and electrically coupled to the receiving electrode line, and the second piezoelectric film is attached to the touch panel and electrically coupled to the transmitting electrode line. An electronic device is also provided.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No.2016112558408, entitled “TOUCH SCREEN WITH FINGERPRINT IDENTIFICATIONFEATURE AND ELECTRONIC DEVICE” filed on Dec. 30, 2016, the contents ofwhich are expressly incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to the field of display technology, andmore particularly relates to a touch screen and an electric device usingthe same.

BACKGROUND OF THE INVENTION

A conventional electronic device, such as a mobile phone and a portableandroid device (PAD), typically includes a fingerprint identificationbutton and a touch screen in response to a user operation. Thefingerprint identification button and the touch screen are separatelyprovided on a main body of the electronic device to achieve their ownfunction. However, this configuration reduces the screen-to-body ratioof electronic device, thereby reducing the user experience.

SUMMARY

According to various embodiments, the present disclosure is directed toa touch screen and an electronic device.

The touch screen include a touch panel and an ultrasonic probe. Thetouch panel includes a first sensing structure including a receivingelectrode line and a second sensing structure including a transmittingelectrode line. The ultrasonic probe includes a first piezoelectric filmand a second piezoelectric film. The first piezoelectric film isattached to the touch panel and electrically coupled to the receivingelectrode line, the second piezoelectric film is attached to the touchpanel and electrically coupled to the transmitting electrode line.

The electronic device includes the touch screen described aforementionedand a main body, the touch screen is mounted on the main body.

The above and other features of the invention including various noveldetails of construction and combinations of parts, and other advantages,will now be more particularly described with reference to theaccompanying drawings and pointed out in the claims. It will beunderstood that the particular method and device embodying the inventionare shown by way of illustration and not as a limitation of theinvention. The principles and features of this invention may be employedin various and numerous embodiments without departing from the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the technical solutions according to the embodiments ofthe present disclosure or in the prior art more clearly, theaccompanying drawings for describing the embodiments or the prior artare introduced briefly in the following. The accompanying drawings inthe following description are only some embodiments of the presentinvention, and persons of ordinary skill in the art can derive otherobvious variations from the accompanying drawings without creativeefforts.

FIG. 1 is a schematic diagram of an electronic device according to anembodiment;

FIG. 2 is a schematic diagram of a touch screen of the electronic deviceaccording to an embodiment;

FIG. 3 is a schematic diagram of the first piezoelectric film and afirst sensing structure according to an embodiment;

FIG. 4 is a schematic diagram of a second piezoelectric film and asecond sensing structure according to an embodiment;

FIG. 5 is a schematic diagram of a first piezoelectric film according toan embodiment;

FIG. 6 is a schematic diagram of a touch screen of the electronic deviceaccording to another embodiment;

FIG. 7 is a schematic diagram of a touch screen of the electronic deviceaccording to yet another embodiment; and

FIG. 8 is a schematic diagram of a touch screen of the electronic deviceaccording to yet another embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The accompanying drawings according to the embodiments of the presentdisclosure will be described in the following to illustrate thetechnical solutions according to the embodiments of the presentdisclosure more clearly and completely. The described implementationsare merely specific embodiments of the present disclosure, and anyimplementations derived from the foregoing implementations withoutcreative efforts by persons skilled in the art shall all fall within theprotection scope of the present disclosure.

As used herein, spatial or directional terms, such as “left”, “right”,“inner”, “outer”, “above”, “below”, “top”, “bottom”, and the like, areunderstood to encompass various alternative orientations and,accordingly, such terms are not to be considered as limiting.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. Thus, a first element could be termed a secondelement without departing from the teachings of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Referring to FIG. 1, an electronic device 100 according to an embodimentincludes a touch screen 10 with a function of fingerprintidentification, a main body 20, a first circuit 30, a processing chip30, a second circuit 40, and a processor 42. In the illustrateembodiment, the electric device 100 is a mobile phone. In an alternativeembodiment, the electric device 100 can be a tablet personal computer, anotebook computer, a smart bracelet, a smart watch or other smartterminals.

Referring to FIG. 2, the touch screen 10 includes a touch panel 11 andan ultrasonic probe 12. The touch panel 11 is of a GFF type and includesa cover plate 13, a first sensing structure 14, and a second sensingstructure 15. The first sensing structure 14 and the second sensingstructure 15 form a capacitive sensing structure. Specifically, thefirst sensing structure 14 and the second sensing structure 15 arerespectively provided with electrodes which form a mutual capacitancewith fingers or form a self-capacitance. When the fingers touch thecover plate 13, the coordinate value of a contact point can be obtainedaccording to a variation of the capacitance, the preset touch functioncan be achieved according to the coordinates or variation thereof.

The first sensing structure 14 includes a plurality of receivingelectrode lines 141 and a first film 143. The first film 143 has a firstsurface 142. The plurality of receiving electrode lines 141 are arrangedequally-spaced on the first surface 142.

In an alternative embodiment, referring to FIG. 3, the first sensingstructure 14 includes a first film 143, a first ITO layer 144, a firstinsulation layer 145, and a plurality of receiving electrode lines 141.The first insulation layer 145, the first ITO layer 144, and the firstfilm 143 are sequentially laminated. The first insulation layer 145 issandwiched between the first ITO layer 144 and the plurality ofreceiving electrode lines 141 to prevent an electrical connectionbetween the plurality of receiving electrode lines 141 and the first ITOlayer 144. At the same time, the first insulation layer 145 is used tocarry the plurality of receiving electrode lines 141, so that theplurality of receiving electrode lines 141 are provided on the firstinsulation layer 145. In addition, a plurality of first pads 146 areformed on the plurality of receiving electrode lines 141 andelectronically coupled to the plurality of receiving electrode lines141.

Referring to FIG. 2, the second sensing structure 15 includes aplurality of transmitting electrode lines 151 and a second film 153. Thesecond film 153 has a second surface 152. The plurality of transmittingelectrode lines 151 are arranged equally-spaced on the second surface152. Thus, the touch screen 10 can achieve fingerprint identification ina full screen range.

In an alternative embodiment, referring to FIG. 4, the second sensingstructure 15 further includes a second film 153, a second ITO layer 154,a second insulation layer 155, and a plurality of transmitting electrodelines 151. The second insulation layer 155, the second ITO layer 154,and the second film 153 are sequentially laminated. The secondinsulation layer 155 is sandwiched between the second ITO layer 154 andthe plurality of transmitting electrode lines 151 to prevent anelectrical connection between the plurality of transmitting electrodelines 151 and the second ITO layer 154. At the same time, the secondinsulation layer 155 is used to carry the plurality of transmittingelectrode lines 151, so that the plurality of transmitting electrodelines 151 are provided on the second insulation layer 155. In addition,a plurality of third pads 156 is formed on the plurality of transmittingelectrode lines 151 and are electrically coupled to the plurality oftransmitting electrode lines 151.

Orthographic projections of the receiving electrode line 141 and thetransmitting electrode line 151 on the cover plate 13 are orthogonal. Inan alternative embodiment, orthographic projections of the receivingelectrode line 141 and the transmitting electrode line 151 on the coverplate 13 are heterotropic.

Referring to FIG. 2, the ultrasonic probe 12 includes a firstpiezoelectric film 16 and a second piezoelectric film 17.

The first piezoelectric film 16 is formed on the receiving electrodeline 141 and is electrically coupled to the receiving electrode line141, so that the touch screen 10 has a more stable structure. The firstpiezoelectric film 16 is used to generate a first piezoelectric signalbased on the piezoelectric effect, and is used to generate ultrasonicaccording to the inverse piezoelectric effect by the piezoelectric pulsesignal.

Referring to FIG. 3, the first piezoelectric film 16 has a third surface163 adjacent to the first sensing structure 14. A plurality of secondpads 164 are formed on the third surface 163 and are electricallycoupled to the first piezoelectric film 16 and the first pads 146,respectively. In addition, the number of the first pads 146 is the sameas the number of the second pads 164.

Referring to FIG. 5, in an alternative embodiment, the firstpiezoelectric film 16 includes a plurality of piezoelectric column 161which are equally spaced, a first filler 162 provided between the firstpiezoelectric column 161. The piezoelectric column 161 generates anelectrical signal or a fingerprint electrical signal under thepiezoelectric effect and is used to determine the pressing position ofthe finger or the fingerprint template. The piezoelectric column 161 maybe made of PVDF, or piezoelectric ceramic transducer (PZT). The numberof the first piezoelectric column 161 is the same as the number of thesecond pads 164, i.e., each second pad 164 is located on a correspondingfirst piezoelectric column 161. The first filler 162 is used to isolatethe piezoelectric column 161 to prevent electrical connection betweenthe piezoelectric column 161. The first filler 162 may be made of epoxyresin, or polytetrafluoroethylene (PTFE). In some embodiments, thecross-sectional shape of the piezoelectric column 161 may be circular,rectangular, polygonal, or other shapes.

Referring to FIG. 2, the second piezoelectric film 17 is formed on thetransmitting electrode line 151 and is electrically coupled to thetransmitting electrode line 151, so that the touch screen 10 has a morestable structure. The second piezoelectric film 17 is used to generatethe first piezoelectric signal based on the piezoelectric effect, and isused to generate ultrasonic according to the inverse piezoelectriceffect by the piezoelectric pulse signal. The second piezoelectric film17 is used to receive the ultrasonic reflected by the finger and thefingerprint template, and is used to generate the first fingerprintelectrical signal according to the piezoelectric effect. In addition, insome embodiments, the material of the second piezoelectric film 17 isconsistent with the material of the first piezoelectric film 16, thatis, the second piezoelectric film 17 also includes a plurality ofequally-spaced second piezoelectric columns (not shown), a second filler(not shown) located between the second piezoelectric column.

Referring to FIG. 4, the second piezoelectric film 17 has a fourthsurface 173 adjacent to the second sensing structure 15. A plurality offourth pads 174 is formed on the fourth surface 173. The plurality offourth pads 174 are electrically coupled to the second piezoelectricfilm 17 and the third pads 156, respectively. In addition, the number offourth pads 174 is the same as the number of the second piezoelectric17, i.e., each fourth pad 174 is located on a corresponding secondpiezoelectric column.

In the illustrated embodiment, the first piezoelectric film 16 and thesecond piezoelectric film 17 are (polyvinylidene fluoride) PVDFpiezoelectric film. Since PVDF piezoelectric film is soft and light inweight, and the matching state is well, PVDF piezoelectric film has highharmonic frequency of the stretching vibration in the thicknessdirection. Thus a wide flat frequency response can be obtained, and thewidth of the frequency response is much better than ordinarypiezoelectric ceramic Energy transducer. Therefore, the firstpiezoelectric film 16 and the second piezoelectric film 17 can convertthe fingerprint pressed against the cover plate 13 into a fingerprintsignal, thereby enabling the touch screen 10 to better recognize thefingerprint information of the fingerprint.

In the illustrated embodiment, the sizes of the first sensing structure14, the second sensing structure 15, the first piezoelectric film 16,and the second piezoelectric film 17 are the same.

Referring to FIG. 2, the touch screen 10 further includes a first solidoptically clear adhesive (OCA) 18 and a second solid OCA 19. The firstsolid OCA 18 is used to bond the cover plate 13 and the firstpiezoelectric film 16. The second solid OCA 19 is used to bond the firstsensing structure 14 and the second piezoelectric film 17. The twoadjacent elements of the touch screen 10 are bonded by OCA or viscose,so that the touch screen 10 has a more stable structure.

In the illustrated embodiment, the first piezoelectric film 16 ispositioned on a side of the first sensing structure 14 adjacent to thecover plate 13. The first sensing structure 14 is positioned on a sideof the first piezoelectric film 16 away from the cover plate 13. Thefirst solid OCA 18 is sandwiched between the cover plate 13 and thefirst piezoelectric film 16. The second piezoelectric film 17 ispositioned on a side of the second sensing structure 15 adjacent to thecover plate 13. The second sensing structure 15 is positioned on a sideof the second piezoelectric film 17 away from the cover plate 13. Thesecond solid OCA 19 is sandwiched between the first sensing structure 14and the second piezoelectric film 17.

In an alternative embodiment, referring to FIG. 6, the firstpiezoelectric film 16 is positioned on a side of the first sensingstructure 14 away from the cover plate 13. The first sensing structure14 is positioned on a side of the first piezoelectric film 16 adjacentto the cover plate 13. The first solid OCA 18 is sandwiched between thecover plate 13 and the first sensing structure 14. The secondpiezoelectric film 17 is positioned on a side of the second sensingstructure 15 away from the cover plate 13. The second sensing structure15 is positioned on a side of the second piezoelectric film 17 adjacentto the cover plate 13. The second solid OCA 19 is sandwiched between thefirst piezoelectric film 16 and the second sensing structure 15.

In an alternative embodiment, referring to FIG. 7, the firstpiezoelectric film 16 is positioned on a side of the first sensingstructure 14 away from the cover plate 13. The first sensing structure14 is positioned on a side of the first piezoelectric film 16 adjacentto the cover plate 13. The first solid OCA 18 is sandwiched between thecover plate 13 and the first sensing structure 14. The secondpiezoelectric film 17 is positioned on a side of the second sensingstructure 15 adjacent to the cover plate 13. The second sensingstructure 15 is positioned on a side of the second piezoelectric film 17away from the cover plate 13. The second solid OCA 19 is sandwichedbetween the first piezoelectric film 16 and the second piezoelectricfilm 17.

In an alternative embodiment, referring to FIG. 8, the firstpiezoelectric film 16 is positioned on a side of the first sensingstructure 14 adjacent to the cover plate 13. The first sensing structure14 is positioned on a side of the first piezoelectric film 16 away fromthe cover plate 13. The first solid OCA 18 is sandwiched between thecover plate 13 and the first piezoelectric film 16. The secondpiezoelectric film 17 is positioned on a side of the second sensingstructure 15 away from the cover plate 13. The second sensing structure15 is positioned on a side of the second piezoelectric film 17 adjacentto the cover plate 13. The second solid OCA 19 is sandwiched between thefirst sensing structure 14 and second sensing structure 15.

Referring to FIG. 1, the processing chip 32 is mounted on the firstcircuit 30. The first circuit 30 is electrically connected the firstpiezoelectric film 16 and the second piezoelectric film 17. The firstcircuit 30 is used to transmit the ultrasonic generated by the firstpiezoelectric film 16 to the second piezoelectric film 17. The firstcircuit 30 is used to transmit the two first piezoelectric signalsgenerated by the first piezoelectric film 16 and the secondpiezoelectric film 17 to the processing chip 32. The first circuit 30 isused to transmit the two first fingerprint signals generated by thefirst piezoelectric film 16 and the second piezoelectric film 17 to theprocessing chip 32. The processing chip 32 is used to process andintegrate the two first piezoelectric signals to form a secondpiezoelectric signal with an intensity boost. The processing chip 32 isused to process and integrate the two first fingerprint signals to forma second fingerprint signal with an intensity boost.

The processor 42 is mounted on the second circuit 40, and the secondcircuit 40 is electrically coupled to the receiving electrode line 141and the transmitting electrode line 151. In some embodiments, the secondcircuit 40 is electrically coupled to the first circuit 30, directly, orby the receiving electrode line 141 and the transmitting electrode line151. The second circuit 40 is used to convert the second piezoelectricsignal into a piezoelectric pulse signal to transmit the piezoelectricpulse signal to the receiving electrode line 141 and the transmittingelectrode line 151 and to transmit the second fingerprint electricalsignal to the processor 42. The processor 42 is used to process andconvert the second fingerprint electrical signal and into a data signal.At the same time, the processor 42 is used to store the data signal inthe electronic device 100 as a fingerprint template or to compare thedata signal with the fingerprint template stored in the electronicdevice 100.

When the user presses the cover plate 13 with a finger, the firstpiezoelectric film 16 and the second piezoelectric film 17 generate thetwo first piezoelectric signals under the piezoelectric effect. The twofirst piezoelectric signals are transmitted to the processing chip 32 bythe first circuit 30 to integrate the second piezoelectric signal. Thesecond piezoelectric signal is transmitted to the second circuit 40 bythe receiving electrode line 141 and the emitter line 151. The secondcircuit 40 processes and convert the second piezoelectric signal intothe piezoelectric pulse signal. The piezoelectric pulse signal istransmitted by the second circuit 40 to the first piezoelectric film 16and the second piezoelectric film 17. The first piezoelectric film 16and the second piezoelectric film 17 will vibrate and generate theultrasonic according to the inverse piezoelectric effect by thepiezoelectric pulse signal. The ultrasonic generated by the firstpiezoelectric film 16 is transmitted by the first circuit 30 to thesecond piezoelectric film 17. The transmitting electrode line 151 canreflect an ultrasonic fingerprint signal after emitting the ultrasonicto the finger or finger template provided on the cover plate 13. Theultrasonic fingerprint signal is received by the first piezoelectricfilm 16 and the second piezoelectric film 17. The two first fingerprintsignals are transmitted to the processing chip 32 by the first circuitto be processed and integrated to form the second fingerprint signal.The second fingerprint signal is transmitted to the processor 42 by thereceiving electrode line 141 and the transmitting electrode line 151 viathe second circuit 40. The processor 42 converts the second fingerprintsignal into the data signal. The processor 42 stores the data signal inthe electronic device 100 as a fingerprint template or compares the datasignal to the fingerprint template stored in the electronic device 100to determine whether the data signal is in accordance with thefingerprint template to perform a preset operation to the electronicdevice.

The electronic device 100 integrates the ultrasonic probe 12 on thetouch panel 11, so that the touch screen 10 of the electronic device 100can realize the touch function of the touch panel 11 and realize thefingerprint identification function of the ultrasonic probe 12. At thesame time, the space of the main body 20 occupied by the ultrasonicprobe 12 can be reduced, thereby improving the experience of the user.

By merits of the first circuit 340 and the processing chip, thecondition that the signals generated by the first piezoelectric film 16and the second piezoelectric film 17 are canceled and have a poorsuperposition effect will be prevented, at the same time, the signalscan have a better superposition effect, thereby enhance the intensity ofthe signals.

The technical features of the embodiments described above can bearbitrarily combined. In order to make the description succinct, thereis no describing of all possible combinations of the various technicalfeatures in the aforementioned embodiments. It should be noted thatthere is no contradiction in the combination of these technical featureswhich should be considered as the scope of the description.

The foregoing implementations are merely specific embodiments of thepresent disclosure, but are not intended to limit the protection scopeof the present disclosure. It should be noted that persons skilled inthe art can understand and embody all or part of flowcharts of the aboveimplementations. Equivalent variation figured out by persons skilled inthe art shall all fall within the protection scope of the presentdisclosure.

What is claimed is:
 1. A touch screen for fingerprint identification,comprising: a touch panel comprising: a cover plate; a first sensingstructure disposed on the cover plate and comprising a receivingelectrode line; and a second sensing structure disposed on the firstsensing structure and comprising a transmitting electrode line; and anultrasonic probe comprising: a first piezoelectric film attached to thetouch panel and electrically coupled to the receiving electrode line;and a second piezoelectric film attached to the touch panel andelectrically coupled to the transmitting electrode line.
 2. The touchscreen of claim 1, wherein the first sensing structure comprises a firstfilm, the receiving electrode line is arranged on the first film, thesecond sensing structure comprising a second film, the transmittingelectrode line is arranged on the second film; the touch screen is afilm electrode (GFF) type touch screen.
 3. The touch screen of claim 1,further comprising a first solid optically clear adhesive (OCA)sandwiched between the cover plate and the first piezoelectric film. 4.The touch screen of claim 1, further comprising a second solid OCAsandwiched between the first piezoelectric film and the second sensingstructure.
 5. The touch screen of claim 1, wherein the firstpiezoelectric film is positioned on a side of the first sensingstructure adjacent to the cover plate, and the second piezoelectric filmis positioned on a side of the second sensing structure adjacent to thecover plate.
 6. The touch screen of claim 1, wherein the firstpiezoelectric film is positioned on a side of the first sensingstructure adjacent to the cover plate; the second piezoelectric film ispositioned on a side of the second sensing structure away from the coverplate.
 7. The touch screen of claim 1, wherein the first piezoelectricfilm is positioned on a side of the first sensing structure away fromthe cover plate; the second piezoelectric film is positioned on a sideof the second sensing structure adjacent to the cover plate.
 8. Thetouch screen of claim 1, wherein the first piezoelectric film ispositioned on a side of the first sensing structure away from the coverplate; the second piezoelectric film is positioned on a side of thesecond sensing structure away from the cover plate.
 9. The touch screenof claim 1, wherein a material constituting the first piezoelectric filmand the second piezoelectric film are made of polyvinylidene fluoride.10. The touch screen of claim 1, wherein orthographic projections of thereceiving electrode line and the transmitting electrode line on thecover plate are orthogonal.
 11. The touch screen of claim 1, whereinorthographic projections of the receiving electrode line and thetransmitting electrode line on the cover plate are heterotropic.
 12. Anelectronic device, comprising: a main body; and a touch screen mountedon the main body, the touch screen comprising: a cover plate; a firstsensing structure disposed on the cover plate and comprising a receivingelectrode line; and a second sensing structure disposed on the firstsensing structure and comprising a transmitting electrode line; and anultrasonic probe comprising: a first piezoelectric film attached to thetouch panel and electrically coupled to the receiving electrode line;and a second piezoelectric film attached to the touch panel andelectrically coupled to the transmitting electrode line.
 13. Theelectronic device of claim 12, further comprising: a first circuitmounted in the main body; and a processing chip mounted on the firstcircuit; wherein the first circuit is electrically coupled to the firstpiezoelectric film and the second piezoelectric film; the first circuitis configured to send two first piezoelectric signals generated from thefirst piezoelectric film and the second piezoelectric film to theprocessing chip; the first circuit is configured to send two firstfingerprint electrical signals generated from the first piezoelectricfilm and the second piezoelectric film to the processing chip; the firstcircuit is configured to send ultrasonic generated from the firstpiezoelectric film to the second piezoelectric film; wherein theprocessing chip is configured to process and integrate the two firstpiezoelectric signals to form a second piezoelectric signal; and theprocessing chip is configured to process and integrate the two firstfingerprint electrical signals to form a second fingerprint electricalsignal.
 14. The electronic device of claim 13, further comprising: asecond circuit mounted in the main body; a processor mounted in the mainbody; wherein the second circuit is electrically coupled to thereceiving electrode line and the transmitting electrode line; the secondcircuit is configured to convert the second piezoelectric signal into apiezoelectric pulse signal and send the piezoelectric pulse signal tothe receiving electrode line and the transmitting electrode line; thesecond circuit is configured to send the second fingerprint electricsignal to the processor; and the processor is configured to process andconvert the second fingerprint electric signal into a data signal. 15.The electronic device of claim 12, wherein the first sensing structurecomprises a first film, the receiving electrode line is arranged on thefirst film, the second sensing structure comprising a second film, thetransmitting electrode line is arranged on the second film; the touchscreen is a film electrode type touch screen.
 16. The electronic deviceof claim 12, wherein the touch screen further comprises a first solidOCA sandwiched between the cover plate and the first piezoelectric film.17. The electronic device of claim 12, wherein the touch screen furthercomprises a second solid OCA sandwiched between the first piezoelectricfilm and the second sensing structure.
 18. The electronic device ofclaim 12, wherein the first piezoelectric film is approximately to aside of the first sensing structure; the second piezoelectric film isapproximately to a side of the second sensing structure.
 19. Theelectronic device of claim 12, wherein the first piezoelectric film isapproximately to a side of the first sensing structure; the secondpiezoelectric film is away from a side of the second sensing structure.20. The electronic device of claim 12, wherein the first piezoelectricfilm is away from a side of the first sensing structure; the secondpiezoelectric film is approximately to a side of the second sensingstructure.